Compensation method and sensitivity analysis of DPHP frozen soil ice content measurement

Abstract

The Duel-Probe-Heat-Pulse (DPHP) ice content sensor can measure the ice content of the soil, but its measurement process is not clear for the disturbance of frozen soil. In this study, the ice content measurement test was carried out for silty clay specimens. Firstly, the influence of heating power was clarified. The variation trends of the temperature rise relaxation area in the respective conditions of the three representative volumetric water content specimens and the degree of compaction of the specimen preparation was compared. Then, the influence of five kinds of heating interval time on the measurement accuracy was explored. Finally, the compensation and analysis method of the temperature relaxation area, based on the temperature of the measuring point and the phase change of ice water, is proposed. The experimental results show that: (1) There is a hysteresis in the temperature rise curve of the probe of the DPHP ice content sensor. In the measurement process, a long enough integral interval should be selected to calculate the temperature relaxation area. (2) For the specimens with the same initial water content, the measured temperature relaxation area increases with the increase of compaction degree, and this trend weakens in the specimens with the increase of water content. (3) The DPHP ice content sensor causes irreversible disturbance to the soil during the measurement process. The temperature relaxation area, obtained by continuous measurement at a short heating interval, is small, and manifests a decreasing trend with the increase of measurement times. (4) It is recommended that the heating interval time should be more than 120 min, and the temperature relaxation area should be compensated when the continuous measurement of short heating interval time is carried out, to offset the influence of the temperature rise of the measuring point. The research results reveals the influence of multiple factors on the measurement of DPHP ice content sensors, which can provide a basis for the accuracy of soil ice content measurement.